415
FXUS65 KBYZ 301546
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
946 AM MDT SAT MAY 30 2026
KEY MESSAGES
- NUMEROUS SHOWERS AND THUNDERSTORMS ALONG WITH A COOLING TREND
THIS WEEKEND.
- MARGINAL RISK (1/5) FOR STRONG TO SEVERE THUNDERSTORMS OVER
SOUTH- EASTERN MONTANA AND NORTH-EASTERN WYOMING TODAY. MAIN
THREATS ARE HEAVY RAIN, STRONG WIND GUSTS OF 60+ MPH, AND HAIL
UP TO HALF DOLLAR SIZE (1.25 INCHES).
- FLASH FLOOD WATCH IS IN EFFECT FOR THE ELK, ROBERTSON DRAW, AND
EAST SIDE BURN AREAS FROM 6AM THIS MORNING UNTIL MIDNIGHT
TONIGHT.
- ACCUMULATING SNOW IS FORECAST OVER 9000 FT THIS WEEKEND. WINTER
CONDITIONS MAY IMPACT THE BEARTOOTH HIGHWAY (MODERATE CHANCE).
UPDATE
MESOANALYSIS AT 1440Z SHOWS A 700MB LOW NEAR PINEDALE, WY AND A
TROF EXTENDING FROM THERE EASTWARD THRU CENTRAL WY. THE DEEP
EASTERLY FLOW/ASCENT IS PRODUCING WAVES OF SHOWERS MOVING EAST TO
WEST THIS MORNING. A CWOP STATION NEAR BIG TIMBER HAS PICKED UP
0.70" OF RAIN IN THE PAST 6 HOURS, WITH OVER A THIRD OF AN INCH
AT LIVINGSTON. THERE IS ANOTHER CLUSTER OF THUNDERSTORMS W/ HEAVY
RAIN MOVING THRU TREASURE AND NORTHERN BIG HORN. ALL TOLD WE ARE
LOOKING AT WAVES OF SHOWERS AND T-STORMS WITH HEAVY RAIN THRU THE
DAY, UNTIL THE MID LEVEL TROF LIFTS NORTH OF US TONIGHT. RISK OF
SEVERE SHOULD BE CONFINED TO THE EAST AS WESTERN AREAS WILL BE
RAIN- COOLED AND CLOUDY (HAVE ACTUALLY LOWERED FORECAST HIGHS A
FEW DEGREES). WILL NEED TO MONITOR HOW THE AIR MASS EVOLVES OVER
OUR EAST INTO THE AFTERNOON. THERE ARE ALSO AREAS OF STRATUS IN
OUR EAST THAT COULD PLAY A ROLE, PERHAPS CREATING DIFFERENTIAL
HEATING BOUNDARIES?
HAVE ADDED THE REMINGTON BURN SCAR (SOUTHERN ROSEBUD CO) TO THE
FLASH FLOOD WATCH WHICH RUNS THROUGH MIDNIGHT TONIGHT. STAY ALERT
TODAY!
CONFIDENCE HAS GROWN FOR SNOW SHOWERS TO DROP FROM 11KFT TO 9KFT
OVER THE BEARTOOTHS TONIGHT. HAVE ISSUED A WINTER WEATHER ADVISORY
FOR WINTRY CONDITIONS (1-3" ACCUMS) OVER THE BEARTOOTH HIGHWAY
FROM MIDNIGHT TONIGHT THROUGH SUNDAY EVENING. IMPACTS WILL BE
MAINLY ABOVE VISTA POINT.
JKL
DISCUSSION
NEXT 7 DAYS (THROUGH THURSDAY)...
AN UPPER LOW OVER THE GREAT BASIN WILL CONTINUE ITS TRACK
NORTHWARD INTO WYOMING TODAY. THIS WILL BRING WIDESPREAD RAINFALL
AND THUNDERSTORMS, WITH A THREAT FOR ISOLATED STRONG TO SEVERE
THUNDERSTORMS IN SOUTHEAST MONTANA. A SURFACE LOW IS EXPECTED TO
DEVELOP OVER NORTHEAST WY AND EXTEND NORTH THROUGH THE ROSEBUD
COUNTY AREA BY LATE MORNING. THIS WILL BE A BOUNDARY FOR DEEP
SOUTHEASTERLY LOW LEVEL MOISTURE FEED TO THE EAST, WITH SYNOPTIC
LIFT AND DEEPER MOISTURE TO THE WEST. CAM'S ARE INDICATING A FEW
ROUNDS OF CONVECTION THROUGH THE DAY. HOW THESE UNFOLD IS
UNCERTAIN GIVEN THE NATURE OF DYNAMIC PROCESSES AS THIS NEGATIVE
TILT WEATHER SYSTEM MOVES INTO OUR REGION WITH EACH WAVES
INFLUENCE ON SUBSEQUENT WAVES DUE TO OUTFLOW FROM CONVECTION. THAT
SAID, WE EXPECT A ROUND IN THE MORNING TO ROTATE COUNTER
CLOCKWISE AROUND THE UPPER LOW COMING FROM NORTHERN WY INTO OUR
CENTRAL ZONES (THINK SHERIDAN COUNTY SWINGING NW TOWARD
YELLOWSTONE COUNTY). IN THE MEANTIME, NUMEROUS SHOWERS AND
EMBEDDED THUNDER WILL DEVELOP OVER THE MOUNTAINS AND FOOTHILLS IN
OUR WESTERN CWA. THIS MORNINGS WAVE MAY PRODUCE MODERATE TO HEAVY
POCKETS OF HEAVY RAIN WITH SCATTERED THUNDERSTORMS. MOST OF THAT
ACTIVITY GENERALLY LIFTS NORTH-NORTHWEST OF BILLINGS BY MIDDAY.
THIS MAY ALLOW FOR A BRIEF BREAK AND SOME SUNSHINE TO INCREASE
DESTABILIZATION/LAPSE RATES OVER OUR SOUTH AND EAST FOR THE NEXT
WAVE OF CONVECTION MOVING UP FROM THE SOUTH ACROSS OUR CWA IN THE
AFTERNOON. BY THIS TIME, MUCAPE VALUES MAY RANGE FROM 500-1000 J/KG
ACROSS OUR CENTRAL AND EAST WITH INCREASING MID LEVEL WINDS.
HELICITY TRACK PROGS ARE NOT TOO IMPRESSIVE FOR OUR AREA ON THE
HRRR, BUT THE RRFS DOES SHOW DECENT HELICITY TRACKS FROM NORTHERN
ROSEBUD TO POWDER RIVER COUNTY AND ALSO THE FALLON/CARTER COUNTY
LINE.
OVERALL, THE INGREDIENTS SUGGEST A MARGINAL ENVIRONMENT FOR SOME
STRONG TO SEVERE THUNDERSTORMS, WHICH SPC CURRENTLY DOES HAVE US
UNDER FOR THE DAY. DAMAGING WINDS 60+ MPH AND HAIL TO 1.25 INCHES
ARE MAIN THREATS. HEAVY RAINFALL WITH STRONGER CELLS IS EXPECTED
AS WELL WITH PWATS REACHING OVER AN INCH ACROSS THE CENTRAL AND
EASTERN PORTIONS OF THE CWA. THE DRIER CONDITIONS WE HAVE SEEN
SHOULD PRECLUDE ANY WIDESPREAD FLASH FLOODING RISK. HOWEVER, THERE
IS CONCERN FOR THE BURN SCARS OF THE ELK FIRE, EAST SIDE AND
ROBERTSON FIRES WHERE THRESHOLDS FOR IMPACTS ARE MUCH LESS. THE
FLASH FLOOD WATCHES FOR THESE BURN SCARS LOOKS GOOD AND GOES FROM
6 AM TODAY TO 12 MIDNIGHT SUNDAY. PEOPLE NEAR BURN SCARS AND
FLOOD PRONE AREAS SHOULD BE ALERT AND HAVE A PLAN IF FLOODING OR
DEBRIS FLOWS OCCUR.
THE HEAVIER THUNDERSTORMS SHOULD LIFT NORTH AND EAST THIS
EVENING, BUT WE WILL TRANSITION TO A PERIOD OF MAINLY SHOWERS
WITH EMBEDDED THUNDER FOR SUNDAY, WITH BEST RAINFALL POTENTIAL
ACROSS THE WEST AND CENTRAL CWA AS THE UPPER LOW DRIFTS OVER US.
SOME SECTIONS IN THE EAST COULD EVEN BE DRY SLOTTED AT TIMES. BY
MONDAY, THE UPPER TROUGH IS PROGGED TO DRIFT FURTHER NORTH WITH
DOWNWARD MOTION AND DRIER AIR MOVING INTO OUR AREA FROM THE SOUTH.
OVERALL PRECIPITATION...THERE IS A MODERATE TO HIGH CHANCE FOR AT
LEAST 0.5" OF RAINFALL ACROSS THE REGION THIS WEEKEND. THE BEST
POTENTIAL IS OVER THE WESTERN PORTIONS OF THE CWA AND TO A LESSER
EXTENT THE SOUTHEAST. THERE IS A SLIGHT RISK FOR EXCESSIVE
RAINFALL OVER CENTRAL MT TODAY. THIS CORRESPONDS TO THE LATEST
HREF 1"/HR RAINFALL PROBABILITIES OF 40-70% FOR A POINT WITHIN
25KM. WHILE THE RISK FOR FLOODING REMAINS LOW OVERALL AT THIS
TIME, THERE COULD BE LOCALIZED CONCERNS DUE TO NEAR STATIONARY
THUNDERSTORMS AND HEAVY RAINFALL, PARTICULARLY OVER THE
AFOREMENTIONED BURN SCARS.
SNOWFALL...AS THE UPPER LOW DRIFTS OVER US TONIGHT INTO SUNDAY,
COOLER AIR WILL BRING SNOW LEVELS DOWN FROM 11KFT TO AROUND 9KT BY
SUNDAY MORNING. AROUND 3-7 INCHES OF ACCUMULATION IS POSSIBLE OVER
THE HIGHER PEAKS ABOVE 10K FT. THE MAJORITY OF ACCUMULATING
SNOWFALL IS FORECAST TONIGHT INTO SUNDAY MORNING. BE PREPARED FOR
POTENTIAL IMPACTS TO THE BEARTOOTH HIGHWAY THIS WEEKEND.
AN AXIS OF BREEZY NORTHWEST WINDS LOOKS TO DEVELOP FROM WESTERN
MT SUNDAY INTO MONDAY. THE LATEST FORECAST HAS WINDS GUSTING IN
THE 25 TO 40 MPH RANGE, WITH GREATER GUSTS APPROACHING 50 MPH
ACROSS THE FOOTHILLS WEST OF BILLINGS.
ENSEMBLES SPREADS INCREASE THE FIRST HALF THE WEEK DUE TO
DISAGREEMENT ON THE EVOLUTION OF THE LINGERING UPPER LOW TO THE
NORTH. FOR NOW, THERE IS A LOW TO MODERATE CHANCE FOR SHOWERS AND
WEAK THUNDERSTORMS MONDAY INTO WEDNESDAY...MOSTLY ACROSS EAST
CENTRAL SECTIONS.
LOOK FOR HIGH TEMPERATURES IN THE 60S TO LOW 80S TODAY, UPPER 50S
TO LOW 70S ON SUNDAY (COOLEST IN THE WEST EACH DAY), 60S TO 70F
ON MONDAY, AND 70S TO 80SF THROUGH THE MIDDLE OF THE WEEK. BT
AVIATION
A WEATHER SYSTEM WILL BRING MULTIPLE ROUNDS OF SHOWERS AND
THUNDERSTORMS TO THE AREA TODAY, ALONG WITH INCREASED CLOUD COVER.
ANY SHOWER OR THUNDERSTORM WILL BE CAPABLE OF PRODUCING BRIEF
MVFR CONDITIONS AND BREEZY WINDS. OVER SOUTH-EASTERN MONTANA INTO
NORTH- EASTERN WYOMING, STRONG TO SEVERE THUNDERSTORMS ARE ALSO
POSSIBLE TODAY (MODERATE CHANCE). THE MAIN CONCERN WITH ANY STRONG
TO SEVERE THUNDERSTORM IS HEAVY RAIN REDUCING VISIBILITY TO IFR,
STRONG WIND GUSTS OF 30 TO 50 KNOTS, AND HAIL UP TO HALF DOLLAR
(1.25 INCHES) SIZE. TONIGHT INTO SUNDAY, SHOWERS AND EMBEDDED
THUNDERSTORMS LOOK TO BECOME MORE WIDESPREAD OVER MUCH OF CENTRAL
AND WESTERN MONTANA AND NORTH- CENTRAL/WESTERN WYOMING. WITH THIS,
LOW (MAINLY MVFR) CEILINGS ARE EXPECTED TO FILL IN WHERE
PRECIPITATION IS OCCURRING. IN ADDITION, EXPECTED FREQUENT
MOUNTAIN OBSCURATIONS TO OCCUR THROUGH THE FORECAST PERIOD.
OTHERWISE, LOW CLOUDS (MVFR) EXIST OVER FAR EASTERN MONTANA,
AROUND KBHK AND K97M, INTO THE DAKOTAS EARLY THIS MORNING. LOOK
FOR THIS CLOUD DECK TO DISSIPATE THIS AFTERNOON. ARENDS
PRELIMINARY POINT TEMP/POPS
TDY SUN MON TUE WED THU FRI
-------------------------------------------------------
BIL 070 052/061 046/070 046/074 048/075 051/077 051/083
+/T 98/W 22/T 31/B 21/B 23/T 31/U
LVM 060 042/057 039/066 039/071 041/075 044/074 043/080
+/T 99/T 35/T 21/B 11/U 35/T 21/U
HDN 073 050/063 043/072 043/075 046/077 048/078 048/083
9/T 88/W 31/B 40/B 10/B 23/T 31/U
MLS 081 054/067 045/070 046/076 049/076 050/078 051/081
7/T 98/T 41/B 41/B 21/B 24/T 31/B
4BQ 080 053/066 045/072 047/077 048/076 050/079 050/081
9/T 77/T 31/U 42/T 31/B 24/T 41/B
BHK 077 052/071 043/069 045/076 047/075 048/076 048/078
7/T 88/T 51/N 54/T 31/B 25/T 42/T
SHR 071 045/063 039/070 040/076 042/076 044/078 044/082
9/T 78/T 34/T 21/U 12/T 24/T 22/T
BYZ WATCHES/WARNINGS/ADVISORIES
MT...FLASH FLOOD WATCH IN EFFECT THROUGH THIS EVENING FOR ZONES
56-58-67.
WINTER WEATHER ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO
MIDNIGHT MDT SUNDAY NIGHT FOR ZONE 67.
WY...FLASH FLOOD WATCH IN EFFECT THROUGH THIS EVENING FOR ZONES
198-199.
WEATHER.GOV/BILLINGS
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